The subject matter disclosed herein generally relates to rotors for aircraft use. More specifically, the subject disclosure relates to rotor head configurations for rotors of helicopters.
A typical rotor for, for example, a helicopter, includes a plurality of blades secured to a rotor hub. One configuration of helicopter rotor is a flex beam rotor head. The flex beam rotor head includes one or more flexible beams to which the plurality of blades are secured. The flex beams are typically constructed to at least partially accommodate blade flap and blade pitch changes of the rotor blades. For rotors having an even number of blades, one configuration of rotor head is referred to as a crossbeam rotor head. The crossbeam rotor head includes flex beams extending through an axis of rotation of the rotor and crossing at the axis of rotation. In a cross beam rotor head, a rotor blade is secured to each end of each flex beam. In a typical cross beam rotor, the flex beams are clamped to each other at the rotor hub and secured thereto. The clamping of the flex beams restrains the pitch motion of the flex beams at the rotor hub, thus the flex beams must be configured to accommodate the entire range of pitch change of the rotor blades over approximately one half of the flex beam's length, from the rotor hub to an attachment point of the rotor blade. Thus, to achieve acceptable service life, the geometry and composite laminate properties of the typical flex beam are modified to handle the blade pitch change, but this results in degraded aerodynamic efficiency of the rotor system given the geometrical constraints of the cross beam rotor head.
The art would well receive a flex beam rotor head which improves the aerodynamic efficiency of the rotor by improving the packaging constraints created by twisting of the flexbeam.